Tdc

What's Cool

TDC

KEVIN CAMERON

WHAT'S COOL IN ENGINEERING? What's cool is when someone, having wrestled with a problem or a set of problems for some time, and having filled his or her head with relevant information, and having rejected countless solutions, suddenly has an answer. Such an answer usually comes with no explanation, no map indicating where it came from or by what path. Just Pop!—a knowledge that this might work.

The book “Engines of Pratt & Whitney” by Jack Connors is full of such things. Before World War II, P&W was having master-connecting-rod big-end bearing failures in its R-1830 radial engine (1830s later powered the DC-3 and the B-24 in very large numbers). Each such bearing carried the loads of seven cylinders, so it was an overworked part. At the time, the bearing surface was silver—a material that offers good compatibility with steel crankpins and fatigue strength beyond that of white metal or copper-lead but is lacking in “forgiveness.” Frequent seizures during high-rpm dives had caused the U.S. Navy—a customer too good to risk losing—to say it would stop buying 1830s if the problem were not fixed promptly.

Engineers hold meetings to discuss such things and spend much of their lives there. One P&W engineer at the time said such meetings were not real discussion, just “men comparing their prejudices.” Back and forth went the dialog, clearances, oil-hole size and shape, alignment. Then, in walked Earl Ryder, a man known to me only through his SAE papers. What a contrast with the modern style, which uses obscure professional (I almost said “priestly”) language to make problems look more, not less, complex. They are advertisements for the author’s “expertise” and invitations to consulting contracts. Ryder’s papers were written clearly, and their goal was to inform: Here’s what we’ve learned!

I once handed a stack of 1950s engineering papers to a visiting Honda engineer. He looked through them and smiled. Then he said, “There was a big change after the 1950s. They became very hard to understand.”

I imagine Ryder walking into the meeting, hands in pockets, jingling his change as men of his generation did.

“Why don’t we put some lead on that bearing?” was his suggestion. His colleagues digested this, that lead acts as a solid lubricant, that its softness would allow wear particles to embed harmlessly.

“How much would you use?” someone asked.

Ryder thought a moment, then said, “Oh, about five-thousandths.”

So it was decided. Getting lead to bond and plate evenly onto the silver were less easy, but a rush program of experiments achieved the result. When these silver-lead bearings were fitted to test engines, they handily passed the Navy’s series of dive/overrev tests. The lead was thick enough to embed and render harmless most particles but thin enough that it could transmit the heavy bearing load to the strong silver beneath without being crushed.

As engines with the new bearings accumulated flight hours, a new problem arose: corrosion of the lead by combustion acids—so-called “hen-tracking.” More meetings were scheduled, and because it had worked before, Ryder was again summoned.

“Looks like we need to put something pretty inert on there to protect the lead,” he said. “How about indium?”

So it was done, and it worked. Grumman F4F “Wildcat” Navy fighters flying from Henderson Field on battle-scarred Guadalcanal were able to employ firing passes in vertical dives as a major combat tactic early in the Pacific War—without master-rod bearing seizures.

You can be sure that Ryder had spent plenty of time thinking through the periodic table of the elements and had not just pulled the two metals, lead and indium, out of the cigarette-smoke-filled air of that East Hartford conference room. It was all working inside his head without his willing it, whether he was driving his car, having a shower or falling asleep at the end of the day. Brains look for patterns in the data we stuff into them, and they look for solutions. That’s how we living critters survive and make sense of our world.

When Yamaha put its Earl Ryder, engineer Masao Furusawa, on the problem of how to make the unsuccessful 2003 YZR-M1 win MotoGP races, he also digested the available information. For some reason, riders on the V-Five Hondas could get on-throttle earlier and harder than could the Yamaha men. The usual solutions—careful suspension work and changes to engine powerband—had produced nothing useful. What was the problem? What was different?

Who knows what Furusawa’s train of thought was? But anyone who has ever turned over a flat-crank inlineFour with a speed handle knows that it takes a “lumpy torque” to turn it. Every 180 degrees, all the pistons are stopped simultaneously—two at TDC, two at BDC, and it takes effort to heave them into motion again for the next halfrevolution. A Vee engine is different because when one of its pistons is stopped at TDC or BDC, the one next to it is mid-stroke, moving fast. There are no “torque lumps” needed to re-accelerate stopped pistons because they can use the energy released as neighboring pistons slow down and stop. A curious engineer would want to convert that feeling into numbers—just how much crank-speed variation, or flutter, would result from all that starting and stopping? This is “doing a sample calculation,” something good engineers do all the time, even just for fun. If the number were large, it could propagate through the driveline and upset rearwheel grip. Could this be the crucial difference between Inlines and Vees?

It evidently looked good enough for Furusawa to order expensive builds of prototype engines with 90-degree (“crossplane”) crankshafts and cams with suitably retimed valve events. Good enough to bet his position and reputation as a problem solver into the bargain.

As with Ryder’s group, struggling with plating baths, a new idea is nothing unless there is the R&D power to grind through the necessary experimentation to success. Even great ideas are useless if they become obsolete before they become hardware.

Crossplane Mis won five MotoGP championships against Vee-engined bikes, 2004, 2005, 2008-2010. That’s cool. Having Valentino Rossi as rider probably didn’t hurt, either. □